ERYLUS ROTUNDUS VAR. TYPICA. 



309 



been different to a certain extent, since they were found at different stations. 

 For this reason, and because the differences between them are not great and 

 their pecuUarities more in the character of individual (somatic) adaptations 

 than of germinal quahties, I think that no greater systematic vahie than that 

 of local forms, two, A and B, in the group megarhabda, and four. A, B, C, and 

 D, in the group typica, can be attached to them. 



The differences between the groups are much greater, and can hardly be 

 directly due to differences in the surroundings, since specimens belonging to 

 different groups were repeatedly captured together, at one and the same sta- 

 tion. This and their general nature lead me to consider the peculiarities, by 

 which these groups differ, not as mere somatic adaptations but as germinal 

 characters. Although most probably germinal in nature and certainly not in- 

 considerable, these differences are, in my opinion, nevertheless insufficient for 

 more than varietal distinction. 



The characters of the three varieties are the following: — 



Var. megarhabda. 



Cortical armour composed chiefly of microrhabds. Rhabd megascleres 

 mostly sharp pointed, blunt forms rare; 330-650 by G-13 fi. Rhabd-clusters 

 absent. Microrhabds gradually and sharply pointed, central tyle small or ab- 

 sent; 43-98 by 3-7.5 fi. Triaenes; rhabdome 170-370 /i long; cladome 160- 

 350 n broad. Acanthtylasters with three or more rays; 12-27 /« in diameter. 

 Oxyasters 7.5-17 /j. in diameter. Aspidasters 55-66 by 46-59 by 4.6-8.8 /<; aver- 

 age proportion of length to breadth to thickness 100 : 90.5 : 10.3. 



South coast of Molokai ; coast of Kauai. 



Var. typica. 



Cortical armour composed chiefly of aspidasters. Rhabd megascleres 

 sharp pointed or blunt amphioxes, or amphistrongyles ; 310-570 by 6-15 

 Rhabd-clusters absent. Microrhabds variously pointed or blunt, with or with- 

 out central tyle; 30-66 by 1.5-4 /(. Triaenes; rhabdome 200-220 /t long ; clad- 

 ome 150-400 /J. broad. Acanthtylasters with three or more rays; 15-31 /< in 

 diameter. Oxyasters 7-16 // in diameter. Aspidasters 50-77 by 48-70 by 

 4.4-7.8 /<; average proportion of length to breadth to thickness 100:94:10.5. 



South coast of Molokai; coast of Kauai; northeast coast of Hawaii. 



